Information encoding for impaired optical path validation

ABSTRACT

A network component comprising at least one processor configured to implement a method comprising transmitting a message to at least one adjacent control plane controller, wherein the message comprises a Type-Length-Value (TLV) having a plurality of parameters, wherein the message comprises frequency dependency information for each of the parameters that is frequency dependent. Included is a method comprising communicating a message comprising a TLV to a control plane controller, wherein the TLV comprises a plurality of parameters and frequency dependency information for each of the parameters that is frequency dependent. Also included is an apparatus comprising a control plane controller configured to communicate a TLV to at least one adjacent control plane controller, wherein the TLV indicates a plurality of parameters and frequency dependency information for each of the parameters that is frequency dependent.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 61/156,282 filed Feb. 27, 2009 by Young Lee, et al.and entitled “Information Encoding for Impaired Optical PathValidation,” which is incorporated herein by reference as if reproducedin its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

BACKGROUND

Wavelength division multiplexing (WDM) is one technology that isenvisioned to increase bandwidth capability and enable bidirectionalcommunications in optical networks. In WDM networks, multiple datasignals can be transmitted simultaneously between network elements (NEs)using a single fiber. Specifically, the individual signals may beassigned different transmission wavelengths so that they do notinterfere or collide with each other. The path that the signal takesthrough the network is referred to as the lightpath. One type of WDMnetwork, a wavelength switched optical network (WSON), seeks to switchthe optical signals with fewer optical-electrical-optical (OEO)conversions along the lightpath, e.g. at the individual NEs, thanexisting optical networks.

One of the challenges in implementing WDM networks is the determinationof the routing and wavelength assignment (RWA) during path computationfor the various signals that are being transported through the networkat any given time. Unlike traditional circuit-switched andconnection-oriented packet-switched networks that merely have todetermine a route for the data stream across the network, WDM networksare burdened with the additional constraint of having to ensure that thesame wavelength is not simultaneously used by two signals over a singlefiber. This constraint is compounded by the fact that WDM networkstypically use specific optical bands comprising a finite number ofusable optical wavelengths. As such, the RWA continues to be one of thechallenges in implementing WDM technology in optical networks.

Path computations can also be constrained due to other issues, such asexcessive optical noise, along the lightpath. An optical signal thatpropagates along a path may be altered by various physical processes inthe optical fibers and devices, which the signal encounters. When thealteration to the signal causes signal degradation, such physicalprocesses are referred to as “optical impairments.” Optical impairmentscan accumulate along the path traversed by the signal and should beconsidered during path selection in WSONs to ensure signal propagation,e.g. from an ingress point to an egress point, with an acceptable amountof degradation.

SUMMARY

In one embodiment, the disclosure includes a network componentcomprising at least one processor configured to implement a methodcomprising transmitting a message to at least one adjacent control planecontroller, wherein the message comprises a Type-Length-Value (TLV)having a plurality of parameters, wherein the message comprisesfrequency dependency information for each of the parameters that isfrequency dependent.

In another embodiment, the disclosure includes a method comprisingcommunicating a message comprising a TLV to a control plane controller,wherein the TLV comprises a plurality of parameters and frequencydependency information for each of the parameters that is frequencydependent.

In yet another embodiment, the disclosure includes an apparatuscomprising a control plane controller configured to communicate a TLV toat least one adjacent control plane controller, wherein the TLVindicates a plurality of parameters and frequency dependency informationfor each of the parameters that is frequency dependent.

These and other features will be more clearly understood from thefollowing detailed description taken in conjunction with theaccompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is nowmade to the following brief description, taken in connection with theaccompanying drawings and detailed description, wherein like referencenumerals represent like parts.

FIG. 1 is a schematic diagram of an embodiment of a WSON system.

FIG. 2 is a schematic diagram of an embodiment of a combined impairmentaware RWA architecture.

FIG. 3 is a schematic diagram of another embodiment of a combinedimpairment aware RWA architecture.

FIG. 4 is a schematic diagram of an embodiment of a separated impairmentaware RWA architecture.

FIG. 5 is a schematic diagram of another embodiment of a separatedimpairment aware RWA architecture.

FIG. 6 is a schematic diagram of another embodiment of a separatedimpairment aware RWA architecture.

FIG. 7 is a schematic diagram of another embodiment of a separatedimpairment aware RWA architecture.

FIG. 8 is a schematic diagram of an embodiment of a distributedimpairment aware RWA architecture.

FIG. 9 is a protocol diagram of an embodiment of the communicationsbetween a NE, a first control plane controller, and a second controlplane controller.

FIG. 10 is a schematic diagram of an embodiment of a link set TLV.

FIG. 11 is a schematic diagram of an embodiment of a connectivity matrixTLV.

FIG. 12 is a schematic diagram of another embodiment of the connectivitymatrix TLV.

FIG. 13 is a schematic diagram for an optical parameter frequencydependence encoding.

FIG. 14 is a schematic diagram of a link set TLV encoding for portparameters.

FIG. 15 is a schematic diagram of a connectivity matrix TLV encoding forport-to-port parameters.

FIG. 16 is a protocol diagram of an embodiment of a path computationcommunication method.

FIG. 17 is a protocol diagram of another embodiment of a pathcomputation communication method.

FIG. 18 is a protocol diagram of another embodiment of a pathcomputation communication method.

FIG. 19 is a schematic diagram of an embodiment of a general-purposecomputer system.

DETAILED DESCRIPTION

It should be understood at the outset that although an illustrativeimplementation of one or more embodiments are provided below, thedisclosed systems and/or methods may be implemented using any number oftechniques, whether currently known or in existence. The disclosureshould in no way be limited to the illustrative implementations,drawings, and techniques illustrated below, including the exemplarydesigns and implementations illustrated and described herein, but may bemodified within the scope of the appended claims along with their fullscope of equivalents.

To ensure proper operations in optical networks, a plurality of networkcomponents (e.g. NEs, subsystems, devices, cabling, etc.) may becharacterized at a detailed level. The detailed characteristics of suchnetwork components may be considered during network planning,installation, and turn-up phases. Additionally, the network componentcharacteristics may be used during day-to-day operations, such as forcomputing and establishing lightpaths and monitoring connections. Thedetailed characteristics may comprise optical impairment due to physicalprocesses in the components.

Disclosed herein are encoding formats for information/parameters used inpath computation and/or optical path impairment validation. Thisencoding is based on International Telecommunication Union (ITU)Telecommunication Standardization Sector (ITU-T) defined optical networkelement characteristics as given in ITU-T recommendation G.680 andrelated specifications. This encoding is intentionally compatible with aprevious impairment free optical information encoding used in opticalpath computations and wavelength assignment.

The units for the various parameters include gigahertz (GHz), decibels(dB), decibels per milliwatt (dBm), milliseconds (ms), picoseconds (ps),and ps/nanometer (nm). These are typically expressed as floating pointnumbers. Due to the measurement limitations inherent in theseparameters, single precision floating point, e.g., 32 bit Institute ofElectrical and Electronics Engineers (IEEE) floating point, numbersshould be sufficient, but are not required.

Optical impairments may be characterized into three groups: (a) thosethat apply to the network element as a whole, (b) those that can vary ona per port basis for a network element, and (c) those that can varybased on ingress to egress port pairs. In addition, some parameters mayalso exhibit frequency dependence. For realistic optical networkelements, per port and port-to-port parameters typically only assume afew different values. For example, the channel gain of a reconfigurableoptical add/drop multiplexer (ROADM) is usually specified in terms ofinput-to-drop, add-to-output, and input-to-output. This implies thatmany port and port-to-port parameters could be efficiently specified,stored and transported by making use of a Link Set TLV (or sub-TLV)and/or a Connectivity Matrix TLV (or sub-TLV) as described herein.However, whether such facilities are used is dependent upon the specificprotocol context, e.g., open shortest path first (OSPF), IntermediateSystem-Intermediate System (IS-IS), etc.

In a TLV structure, the type and length fields form a “header” of sorts.From the type field the following may be inferred: 1) units of theparameter (e.g., dB, dBm, GHz, ps, etc.); 2) the grouping of theparameters (e.g., maximum and minimum values may be grouped); and 3)whether the parameter may exhibit frequency dependency. The encodingdescribed herein provides a compact way to provide optical impairmentparameters. In addition, the frequency range of such parameters may berepresented. Further, frequency dependent impairment parameters may bedifferentiated from frequency independent impairment parameters.Moreover, chromatic dispersion may be encoded using an interpolationtechnique.

In at least some embodiments, the encoding described herein may beimplemented with methods and systems for extending a path computationelement (PCE) protocol (PCEP) to support Impairment aware RWA (IA-RWA)in optical networks, such as WSONs. The IA-RWA may be managed at acontrol plane of the network. A plurality of network protocols, such asthe PCEP and Generalized Multi-Protocol Label Switching (GMPLS), may beused to perform impairment aware path computation based on the networkcomponent characteristics and the expected impact of impairments onlight propagation. A plurality of architectures may be used to implementIA-RWA in the network, which may comprise combined routing, wavelengthassignment (WA), and impairment validation (IV) architectures, separaterouting, WA, and IV architectures, and a distributed WA and IVarchitecture.

FIG. 1 illustrates one embodiment of a WSON system 100. The system 100may comprise a WSON 110, a control plane controller 120, and a PCE 130.The WSON 110, control plane controller 120, and PCE 130 may communicatewith each other via optical, electrical, or wireless means. The WSON 110may comprise a plurality of NEs 112 coupled to one another using opticalfibers. In an embodiment, the optical fibers may also be considered NEs112. The optical signals may be transported through the WSON 110 overlightpaths that may pass through some of the NEs 112. In addition, someof the NEs 112, for example those at the ends of the WSON 110, may beconfigured to convert between electrical signals from external sourcesand the optical signals used in the WSON 110. Although four NEs 112 areshown in the WSON 110, the WSON 110 may comprise any quantity of NEs112.

The WSON 110 may be any optical network that uses active or passivecomponents to transport optical signals. The WSON 110 may implement WDMto transport the optical signals through the WSON 110, and may comprisevarious optical components as described in detail below. The WSON 110may be part of a long haul network, a metropolitan network, or aresidential access network.

The NEs 112 may be any devices or components that transport signalsthrough the WSON 110. In an embodiment, the NEs 112 consist essentiallyof optical processing components, such as line ports, add ports, dropports, transmitters, receivers, amplifiers, optical taps, and so forth,and do not contain any electrical processing components. Alternatively,the NEs 112 may comprise a combination of optical processing componentsand electrical processing components. At least some of the NEs 112 maybe configured with wavelength converters, optical-electrical (OE)converters, electrical-optical (EO) converters, OEO converters, orcombinations thereof. However, it may be advantageous for at least someof the NEs 112 to lack such converters as such may reduce the cost andcomplexity of the WSON 110. In specific embodiments, the NEs 112 maycomprise optical cross connects (OXCs), photonic cross connects (PXCs),optical add/drop multiplexers (OADMs), type I or type II ROADMs,wavelength selective switches (WSSs), fixed optical add/dropmultiplexers (FOADMs), or combinations thereof.

The NEs 112 may be coupled to each other via optical fibers. The opticalfibers may be used to establish optical links and transport the opticalsignals between the NEs 112. The optical fibers may comprise standardsingle mode fibers (SMFs) as defined in the ITU-T standard G.652,dispersion shifted SMFs as defined in ITU-T standard G.653, cut-offshifted SMFs as defined in ITU-T standard G.654, non-zero dispersionshifted SMFs as defined in ITU-T standard G.655, wideband non-zerodispersion shifted SMFs as defined in ITU-T standard G.656, orcombinations thereof. These fiber types may be differentiated by theiroptical impairment characteristics, such as attenuation, chromaticdispersion, polarization mode dispersion, four wave mixing, orcombinations thereof. These effects may be dependent upon wavelength,channel spacing, input power level, or combinations thereof. The opticalfibers may be used to transport WDM signals, such as course WDM (CWDM)signals as defined in ITU-T G.694.2 or dense WDM (DWDM) signals asdefined in ITU-T G.694.1. All of the standards described herein areincorporated herein by reference. The network layer where the NEs 112operate and communicate may be referred to as the transport plane.

The control plane controller 120 may coordinate activities within theWSON 110. Specifically, the control plane controller 120 may receiveoptical connection requests and provide lightpath signaling to the WSON110 via Multiprotocol Label Switching Traffic Engineering (MPLS-TE) orGMPLS, thereby coordinating the NEs 112 such that data signals arerouted through the WSON 110 with little or no contention. In addition,the control plane controller 120 may communicate with the PCE 130 usingPCEP to provide the PCE 130 with information that may be used for thepath computation, and/or receive the path computation from the PCE 130and forward the path computation to the NEs 112. The control planecontroller 120 may be located in a component outside of the WSON 110,such as an external server, or may be located in a component within theWSON 110, such as a NE 112. The network layer where the control planecontroller 120 operates may be referred to as the control plane, whichmay be separated from and may manage the transport plane.

The PCE 130 may perform all or part of the RWA for the WSON system 100,e.g. at the control plane. Specifically, the PCE 130 may receive thewavelength or other information that may be used for the RWA from thecontrol plane controller 120, from the NEs 112, or both. The PCE 130 mayprocess the information to obtain the RWA, for example by computing theroutes or lightpaths for the optical signals, specifying the opticalwavelengths that are used for each lightpath, and determining the NEs112 along the lightpath at which the optical signal should be convertedto an electrical signal or a different wavelength. The RWA may includeat least one route for each incoming signal and at least one wavelengthassociated with each route. The PCE 130 may then send all or part of theRWA information to the control plane controller 120 or directly to theNEs 112. To assist the PCE 130 in this process, the PCE 130 may comprisea global traffic-engineering database (TED), a RWA information database,an optical performance monitor (OPM), a physical layer constraint (PLC)information database, or combinations thereof. The PCE 130 may belocated in a component outside of the WSON 110, such as an externalserver, or may be located in a component within the WSON 110, such as aNE 112.

In some embodiments, the PCE 130 may receive a path computation requestfrom a path computation client (PCC). The PCC may be any clientapplication requesting a path computation to be performed by the PCE130. The PCC may also be any network component that makes such arequest, such as the control plane controller 120, or any NE 112, suchas a ROADM or a FOADM. Generally, the PCC communicates with the PCE 130using PCEP, although other acceptable communication protocols may beused as well.

There may be many types of path computation constraints that can affectthe path computation at the PCE 130. The patch computation constraintsmay be included in the path computation request by the PCC. In oneembodiment, the path computation constraints include optical qualityconstraints. Examples of such include the optical signal-to-noise ratio(OSNR), amplifier spontaneous emission (ASE), polarization modedispersion (PMD), polarization-dependent loss (PDL), coherent opticalcrosstalk, incoherent optical crosstalk, effective pass-band, gainnon-uniformity, gain transients, chromatic dispersion, or combinationsthereof. In some embodiments, the path computation constraints may beclassified as linear in that their effects are independent of theoptical signal power and they affect the wavelengths individually.Alternatively, the path computation constraints may be classified asnonlinear in that their effects are dependent of the optical signalpower, generate dispersion on a plurality of wavelength channels, inducecrosstalk between wavelength channels, or combinations thereof.Regardless, the path computation constraints may be communicated to thePCE 130 so that the PCE 130 may consider them when computing a signal'spath through the WSON 100.

The path computation information used in the WSON system 100 may alsocomprise impairment information, which may be used to perform IA-RWA inthe WSON 110. For instance, the PCE 130 may perform all or part of IVfor the WSON system 100, which may comprise validating a computed pathbased on any impairment in the path that may degrade a propagatedoptical signal. When optical impairments accumulate along a pathpropagated by an optical signal, the impairments may degrade the signal,which may decrease a bit error rate (BER) of the signal or even lead tofailure in detecting or demodulating the signal. The path may bevalidated if the BER of the signal (or any other measure of signalquality) due to optical impairments may be acceptable or tolerated andthe signal may be detected with sufficient accuracy. However, if the BERof the signal is substantially low due to optical impairments, the pathmay be rejected or excluded from the allowed paths.

The optical impairments may be influenced by physical processes orconditions of the network components, such as the type of fiber, thetypes and locations of NEs 112, the presence of other optical signalsthat may share a fiber segment along the signal's path, or combinationsthereof. The optical impairments and the physical processes that maycause such impairments are described in a plurality of opticalcommunications references, such as the Internet Engineering Task Force(IETF) Request for Comments (RFC) 4054, which is incorporated herein byreference as if reproduced in its entirety. Optical impairments are alsodescribed by Govind P. Agrawal in “Fiber-Optic Communications Systems,”published by Wiley-Interscience, 2002, and in “Nonlinear Fiber Optics,”published by Academic Press, 2007, both of which are incorporated hereinby reference.

Optical impairments may be ignored in some networks, where every pathmay be valid for the permitted signal types in the network. In thiscase, optical impairments may be considered during network design andthen ignored afterwards, e.g. during path computation. However, in othernetworks, e.g. larger networks, it may not be practical to limit theallowed paths for each signal type. Instead, IV may be performed for aplurality of paths using approximation techniques, such as link budgetsand dispersion (rise time) budgets, e.g. during path computation.Approximation techniques for IV are described in a plurality of opticalreferences, including ITU-T G.680 and ITU-T series G supplement 39(G.Sup39), both of which are is incorporated herein by reference. Theapproximation techniques for IV may be based on impairment models andmay be used to approximate or estimate impairments due to networkcomponents (such as NEs), e.g. at the control plane level. For instance,approximated IV may comprise determining which paths may have anacceptable BER or OSNR for a signal type. In some cases, IA-RWA may beimproved in the network by combining approximated IV with RWA, e.g. at aPCE, as described below.

In some cases, impairment effects may require accurate estimation, suchas for the evaluation of impairment impact on existing paths prior tothe addition of a new path. A plurality of methods may be used foraccurate or detailed IV, such as methods based on solving a plurality ofpartial differential equations that describe signal propagation in afiber. The methods may also comprise using detailed models for thenetwork components. The estimation/simulation time of such methods maydepend on the situation or condition in the network. A significantamount of time may be needed to validate or qualify a path usingdetailed IV. To increase the probability of validating a path,approximated IV may be performed before the detailed IV. Since detailedIV may be based on estimation/simulation methods that may besubstantially different than the RWA methods, the detailed IV processmay be separated from the RWA process, e.g. using a separate IV entityor a separate PCE.

Some path computation information, such as RWA information, may beshared without restrictions or constraints between the path computationentities, e.g. between a PCE and a PCC or between PCEs. However, in somecases, the impairment information may be private information and may notbe shared between different vendors of different components in thenetwork. For instance, the impairment information may not be shared ifsome proprietary impairment models are used to validate paths or avendor chooses not to share impairment information for a set of NEs. Forexample, in a network that comprises a line segment that corresponds toa first vendor and traverses through a plurality of NEs (e.g. OADMs,PXCs, etc.) that correspond to a plurality of second vendors, theimpairment information for the line segment may be private and may notbe shared with the second vendors. However, the impairment informationfor the second vendors may be public and may be shared with the firstvendor.

In an embodiment, to maintain impairment information of a first vendorequipment private, the first vendor equipment may provide a list ofpotential paths to a first PCE in the network, which may consider thelist for path computation between an ingress node and an egress node.The list of paths may also comprise wavelength constraints and possiblyshared impairment information, e.g. for the first vendor and at least asecond vendor. The list may then be sent to a second PCE in the networkto perform IA-RWA. However, in relatively larger networks, the list ofpaths may be substantially large, which may cause scaling issues. Inanother embodiment, the first vendor equipment may comprise a PCE-likeentity that provides the list of paths to a PCE in the network in chargeof IA-RWA. The PCE-like entity may not perform RWA and therefore may notrequire knowledge of wavelength availability information. This approachmay reduce the scaling issues due to forwarding substantially largelists. In another embodiment, the first vendor equipment may comprise aPCE, which may be configured to perform IA-RWA, e.g. on behalf of thenetwork. This approach may be more difficult to implement than the otherapproaches but may reduce the amount of information exchanged and thequantity of path computation entities involved.

Further, a plurality of IV schemes may be used for IA-RWA, e.g. based ondifferent detail levels and/or different architectures. For instance,the IA-RWA process may comprise IV for candidate paths, where a set ofpaths (e.g. between two nodes) may be validated in terms of acceptableoptical impairment effects. Thus, the validated paths may be providedwith associated wavelength constraints. The paths and the associatedwavelengths may or may not be available in the network when provided,e.g. according to the current usage state in the network. The set ofpaths may be provided in response to a received request for at most K(where K is an integer) valid paths between two nodes. The set of pathsmay be provided without disclosing private impairment information abouta vendor's equipment. Additionally or alternatively, the IA-RWA processmay comprise detailed IV (IV-Detailed), where a validation request for apath and an associated wavelength may be submitted. The path and theassociated wavelength may then be validated and a response may beprovided accordingly. Similar to the case of IV for candidate paths, theIV response may not disclose impairment information about the vendor'sequipment.

Alternatively, the IA-RWA process may comprise distributed IV, whereapproximated impairment degradation measures may be used, such as OSNR,differential group delay (DGD), etc. The approximated measures may becarried through and accumulated along a path, e.g. using GMPLS or othersignaling protocol. When the accumulated measures reach a destinationnode, a final decision may be made about the path validity. Thisapproach may require disclosing impairment information about a vendor'sequipment, e.g. along the path.

A plurality of IA-RWA architectures may be used in optical networks,e.g. WSONs, to perform routing, WA, and IV. FIG. 2 illustrates anembodiment of a combined IA-RWA architecture 200. In the combined IA-RWAarchitecture 200, a PCC 210 may send a path computation request, whichmay comprise path computation information, to a PCE 220. The pathcomputation request may comprise RWA information and the PCE 220 mayhave previous knowledge of shared impairment information, e.g. for aplurality of vendors' equipment. However, the PCE 220 may requestadditional impairment information, such as non-shared impairmentinformation for any additional vendor's equipment. The PCE 220 may thenperform combined routing, WA, and IV using the RWA information and theimpairment information. The PCE 220 may use a single computation entity,such as a processor, to perform the combined IA-RWA. For example, theprocessor may process the RWA information and the impairment informationusing a single or multiple algorithms to compute the lightpaths, toassign the optical wavelengths for each lightpath, and to validate thelightpaths. Alternatively, the PCE 220 may use a plurality of processorsto compute and validate the lightpaths and assign the wavelengths.

During the IA-RWA process, the PCE 220 may perform approximated IV ordetailed IV to validate the lightpaths, as described above. Further, thePCE 220 may perform IV before RWA. As such, the PCE 220 may generatefirst a list of candidate and valid paths in terms of acceptableimpairment effects, and then perform RWA to provide computed paths basedon the list. Alternatively, the PCE 220 may perform RWA before IV, wherea list of computed paths may be first obtained and where then each pathmay be validated based on impairment information.

The amount of RWA information and impairment information needed by thePCE 220 to compute the paths may vary depending on the algorithm used.If desired, the PCE 220 may not compute the paths until sufficientnetwork links are established between the NEs or when sufficient RWAinformation and impairment information about the NEs and the networktopology is provided. The PCE 220 may then send the computed paths, andthe wavelengths assigned to the paths, to the PCC 210. The PCE responsemay not disclose impairment information about a vendor's equipment. Thecombined IA-RWA architecture 200 may improve the efficiency of IA-RWA,and may be preferable for network optimization, smaller WSONs, or both.

FIG. 3 illustrates an embodiment of another combined IA-RWA architecture300. In the combined IA-RWA architecture 300, a PCC 310 may send a pathcomputation request to a first PCE 320. The first PCE 320 may beconfigured to perform routing, WA, and IV for candidate paths(IV-Candidates). The first PCE 320 may use the RWA information in thepath computation request to perform a combined IA-RWA. The first PCE 320may have previous knowledge of shared impairment information for aplurality of vendors' equipment but may request additional impairmentinformation, such as non-shared impairment information for anyadditional vendor's equipment. The impairment information may comprise aset of K paths, e.g. between a source node and a destination node, and aplurality of wavelengths associated with the paths. The first PCE 320may generate a set of validated paths based on the impairmentinformation, e.g. using IV approximation techniques. The first PCE 320may perform RWA based on the generated set of validated paths. The firstPCE 320 may then send a list of computed and validated paths andassigned wavelength to a second PCE 322 (or IV entity), which may beconfigured to perform detailed IV (IV-Detailed).

The second PCE 322 may have previous knowledge of impairment informationthat may not be shared with the first PCE 320 and may use the impairmentinformation to validate the paths. Additionally, the second PCE 322 mayrequest additional impairment information, such as non-shared impairmentinformation for any additional vendor's equipment. Thus, the second PCE322 may validate each computed path and return a final list of validatedpaths to the first PCE 320, which may then forward the list to the PCC310. The final list of validated paths may not comprise the privateimpairment information.

In an alternative embodiment, the first PCE 320 may communicate with thesecond PCE 322 as many times as needed to check the validity of eachcomputed path. For instance, the first PCE 320 may send a validationrequest for each computed path to the second PCE 322, and the second PCE322 may return a positive or negative response for each request to thefirst PCE 320, based on the outcome of a detailed IV process. As such,the first PCE 320 may not obtain any private impairment information inthe response from the second PCE 322.

The combined IA-RWA architecture 300 may be used in the case where thefirst PCE 320, the second PCE 322, or both may access private impairmentinformation about a vendor's equipment but may not share it. Further,separating the IV process into an initial approximated IV and asubsequent detailed-IV between the first PCE 320 and the second PCE 322may improve the efficiency and precision of IA-RWA.

FIG. 4 illustrates an embodiment of a separated IA-RWA architecture 400.In the separated IA-RWA architecture 400, a PCC 410 may send a pathcomputation request to a first PCE (or IV entity) 420, which may beconfigured to perform IV using approximate or detailedtechniques/models. The first PCE 420 may have previous knowledge ofshared impairment information for a plurality of vendors' equipment butmay obtain additional impairment information, such as non-sharedimpairment information for any additional vendor's equipment. The firstPCE 420 may use the impairment information and possibly a set ofavailable wavelengths in the path computation request to generate a listof validated paths. For instance, the impairment information maycomprise a set of about K paths, e.g. between a source node and adestination node, and a plurality of wavelengths associated with thepaths. The first PCE 420 may generate a set of validated paths based onthe impairment information. The first PCE 420 may send the list of pathsand the associated wavelengths to the second PCE 422, e.g. withoutsharing the impairment information with the second PCE 422 or any otherPCE.

The second PCE 422 may be configured to assign wavelengths to the pathsprovided by the first PCE 420 and may then send the list of paths to athird PCE 424, which may be configured for routing assignments. Thethird PCE 424 may receive the path computation information from the PCC410 and perform path computation using the information from the PCC 410and the information from the first PCE 420 and second PCE 422 to obtaina plurality of computed and validated paths and correspondingwavelengths. The third PCE 424 may then send the computed paths andassigned wavelengths to the PCC 410.

In an alternative embodiment, the third PCE 424 may receive the pathcomputation request from the PCC 410 and generate a list of computedpaths and corresponding wavelengths, which may be sent to the second PCE422. The second PCE 422 may assign wavelengths to the paths andcommunicate the list of paths and wavelengths to the first PCE 420 tovalidate each path. For instance, the first PCE 420 may send a positiveor negative response for each computed path, e.g. without sharingprivate impairment information. Finally, the validated paths andassociated wavelength may be sent to the PCC 410, via any of the PCEs.

FIG. 5 illustrates an embodiment of another separated IA-RWAarchitecture 500. In the separated IA-RWA architecture 500, a PCC 510may send a path computation request to a first PCE (or IV entity) 520,which may be configured to perform IV using approximate or detailedtechniques/models and send a list of validated paths and correspondingwavelengths to a second PCE 522, e.g. in a manner similar to theseparated IA-RWA architecture 400. However, the second PCE 522 may beconfigured to perform combined RWA, e.g. using a shared processor ordedicated processors. Thus, the second PCE 522 may receive the pathcomputation information from the PCC 510 and perform path computationusing the information from the PCC 510 and the information from thefirst PCE 520 to obtain a plurality of computed and validated paths andcorresponding wavelengths. The second PCE 522 may then send the computedpaths and assigned wavelengths to the PCC 510. Separating the IV processand the RWA process between the first PCE 520 and the second PCE 522 maybe advantageous since the two different processes may be offloaded assuch to two separate and specialized processing entities, which mayimprove computation efficiency.

In an alternative embodiment, the second PCE 522 may receive the pathcomputation request from the PCC 510 and generate a list of computedpaths and corresponding wavelengths. The second PCE 522 may thencommunicate the list of paths and wavelengths to the first PCE 520 tovalidate each path. For instance, the first PCE 520 may send a positiveor negative response for each computed path, e.g. without sharingprivate impairment information. Finally, the validated paths andassociated wavelength may be sent to the PCC 510, via any of the PCEs.

FIG. 6 illustrates an embodiment of another separated IA-RWAarchitecture 600. In the separated IA-RWA architecture 600, a PCC 610may send a path computation request to a first PCE (or IV entity) 620,which may be configured to perform IV for candidate paths. The first PCE620 may have previous knowledge of shared impairment information for aplurality of vendors' equipment but may request additional impairmentinformation, such as non-shared impairment information for anyadditional vendor's equipment. The first PCE 620 may use the impairmentinformation, and possibly a set of available wavelengths in the pathcomputation request, to generate a list of validated paths. Forinstance, the impairment information may comprise a set of about Kpaths, e.g. between a source node and a destination node, and aplurality of wavelengths associated with the paths. The first PCE 620may generate a set of validated paths based on the impairmentinformation, e.g. using IV approximation techniques. The first PCE 620may send the list of paths and the associated wavelengths to the secondPCE 622. However, the first PCE 620 may not share the impairmentinformation with the second PCE 622.

The second PCE 622 may be configured to perform combined RWA, e.g. usinga shared processor or dedicated processors. The second PCE 622 mayreceive the path computation information from the PCC 610 and performpath computation using this information and the information from thefirst PCE 620 to obtain a plurality of computed and validated paths andcorresponding wavelengths. The second PCE 622 may then send a list ofcomputed and validated paths and assigned wavelength to a third PCE (orIV entity) 624, which may be configured to perform detailed IV.

The third PCE 624 may have previous knowledge of impairment informationthat may not be shared with the second PCE 622 and may use theimpairment information to validate the paths. Additionally, the thirdPCE 624 may request additional impairment information, such asnon-shared impairment information for any additional vendor's equipment.Thus, the third PCE 624 may validate each computed path and return afinal list of validated paths to the second PCE 622. The second PCE 622or the first PCE 620 may then forward the final list to the PCC 610. Thefinal list of validated paths may not comprise the private impairmentinformation.

In an alternative embodiment, the second PCE 622 may communicate withthe third PCE 624 as many times as needed to check the validity of eachcomputed path. For instance, the second PCE 622 may send a validationrequest for each computed path to the third PCE 624, and the third PCE624 may return a positive or negative response to the second PCE 622,based on the outcome of a detailed IV process. As such, the second PCE622 may not obtain any private impairment information in the responsefrom the third PCE 624.

The combined IA-RWA architecture 600 may be used in the case where thefirst PCE 620 and/or the third PCE 624, but not the second PCE 622, mayaccess private impairment information about a vendor's equipment but maynot share it. Further, separating the IV process into an initialapproximated IV and a subsequent detailed IV between the first PCE 620and the third PCE 624 may improve the efficiency and precision ofIA-RWA.

FIG. 7 illustrates an embodiment of another separated IA-RWAarchitecture 700. In the separated IA-RWA architecture 700, a PCC 710may send a path computation request to a first PCE 720, which may beconfigured for routing assignments. The first PCE 720 may perform pathcomputation using path computation information from the PCC 710 and thensend the computed paths and any RWA information in the path computationrequest to the second PCE 722, which may be configured for combined WAand IV.

The second PCE 722 may receive the computed paths and RWA informationfrom the first PCE 720 and may have previous knowledge of sharedimpairment information, e.g. for a plurality of vendors' equipment. Thesecond PCE 722 may also request additional impairment information, suchas non-shared impairment information for any additional vendor'sequipment. Thus, the second PCE 722 may perform combined WA and IV usingthe RWA information and the impairment information. The second PCE 722may use a single, or a plurality of, processors to perform the combinedWA and IV. The second PCE 722 may perform approximated IV or detailed IVto validate the computed paths. Further, the second PCE 722 may performIV before WA. As such, the second PCE 722 may generate first a list ofcandidate and valid paths, e.g. based on the computed paths, and thenperform WA. Alternatively, the second PCE 722 may perform WA before IV,where wavelengths may be assigned to the computed paths and then eachpath may be validated based on impairment information. Since the IVprocess is wavelength dependent, combining WA and IV in the second PCE722 may improve the computation efficiency in the system. The final listof computed paths and assigned wavelengths may then be sent to the PCC710 via the second PCE 722 or the first PCE 720.

In an alternative embodiment, the second PCE 722 may receive the pathcomputation request from the PCC 710 and generate a list of validatedpaths and assigned wavelengths, which may be sent to the first PCE 720.The first PCE 720 may then compute a plurality of paths and associatedwavelengths based on the information from the first PCE 722. Finally,the computed and validated paths and associated wavelengths may be sentto the PCC 710, via any of the PCEs.

FIG. 8 illustrates an embodiment of a distributed IA-RWA architecture800. In the distributed IA-RWA architecture 800, a PCE 810 may receivesome or all of the RWA information from the NEs 820, 830, and 840,perhaps via direct link, and perform the routing assignment. The PCE 810then directly or indirectly passes the routing assignment to theindividual NEs 820, 830, and 840, which may then perform distributed WAand IV (WA/IV) at the local links between the NEs 820, 830, and 840,e.g. based on local information.

For instance, the NE 820 may receive local RWA information from the NEs830 and 840 and send some or all of the RWA information to the PCE 810.The PCE 810 may compute the lightpaths using the received RWAinformation and send the list of lightpaths to the NE 820. The NE 820may use the list of lightpaths to identify the NE 830 as the next NE inthe lightpath. The NE 820 may establish a link to the NE 830, e.g. via asignaling protocol, and use the received local RWA information that maycomprise additional constraints to assign a wavelength for transmissionover the link. Additionally, the NE 820 may use local impairmentinformation to perform IV and generate a list of validated lightpaths.The list of validated paths may correspond to a plurality ofwavelengths, which may be specified by the PCE 810 or indicated in theRWA information. The NE 820 may perform approximated IV for at leastsome of the wavelengths based on approximated models and measures, whichmay be carried through and accumulated along a path, e.g. using GMPLS orGMPLS resource reservation protocol (RSVP). For example, the NE 820 mayperform IV based on a measure of signal quality, e.g. BER or OSNR, whichmay be accumulated along the path by the subsequent nodes.

The NE 830 may receive the list of lightpaths and the wavelengths fromthe NE 820, and use the list of lightpaths to identify the NE 840 as thenext NE in the lightpath. Hence, the NE 830 may establish a link to theNE 840 and assign the same or a different wavelength for transmissionover the link. The NE 830 may also use the same impairment informationused by the node 820 and/or other local impairment information toperform IV and update the list of validated lightpaths and theassociated wavelengths. The NE 830 may perform approximated IV based onthe same approximated models and measures (e.g. BER, OSNR, etc.), whichmay be updated and further accumulated by the node 830. Similarly, theNE 840 may receive the list of lightpaths and wavelengths from the NE830 and the impairment information, including the accumulated measures,from the node 840, update the received information, and propagate theinformation along the path.

Thus, the signals may be routed while the wavelengths are assigned andthe lightpaths are validated in a distributed manner between the NEsuntil a destination node is reached. Assigning the wavelengths at theindividual NEs may reduce the amount of RWA information and impairmentinformation that may be forwarded between the NEs and between the NEsand the PCE 810. However, such distributed WA/IV schemes may requiresharing some local and private impairment information between the NEs.Further, such signaling based schemes may become less practical as thequantity of computed paths and the available wavelengths increase.

At least some of the IA-RWA architectures described above may requirechanges in current protocols and/or standards, for example regarding thePCE, signaling, the information model, routing, or combinations thereof.Table 1 illustrates some aspects of the system that may require changesto support the IA-RWA architectures above.

TABLE 1 Infor- Sig- mation IA-RWA Architecture PCE naling Model RoutingCombined IA-RWA architectures 200 Yes No Yes Yes Combined IA-RWAarchitectures 300 Yes No Yes Yes Combined IA-RWA architectures 400 No NoYes Yes Combined IA-RWA architectures 500 No No Yes Yes Combined IA-RWAarchitectures 600 No No Yes Yes Combined IA-RWA architectures 700 No NoYes Yes Combined IA-RWA architectures 800 No Yes Yes No

Some of the impairment models, which may be used in the IA-RWAarchitectures above, may be described in ITU-T G.680. ITU-T G.680includes some detailed and approximate impairment characteristics forfibers and various devices and subsystems. ITU-T G.680 also describes anintegrated impairment model, which may be used to support IA-RWA, e.g.in the architectures above. However, the impairment characteristics andmodels in ITU-T G.680 are suitable for a network that comprises a linesegment for a first vendor, which passes through a plurality of NEs(e.g. OADMs, PXCs, etc.) for a plurality of second vendors. Theimpairment information for the line segment may be private and theimpairment information for the second vendors may be public. However,additional or different impairment models and impairment characteristicsmay be required for other network configurations, where a plurality ofline segments or systems that correspond to a plurality of vendors maybe deployed across the system.

For instance, in the case of a distributed IA-RWA architecture, such asthe distributed IA-RWA architecture 800, an impairment information modeland an impairment “computation model” may be needed to enable IV.Further, the accumulated impairment measures, which may be propagatedand updated at a plurality of nodes along a path, may requirestandardization so that different nodes for different vendors in thesame system may support IV. ITU-T G.680 may describe some impairmentmeasures that may be used, such as computation formulas for OSNR,residual dispersion, polarization mode dispersion/polarization dependentloss, effects of channel uniformity, etc. However, ITU-T G.680 does notspecify which measurements may be stored or maintained in the nodes andin what form.

The different IA-RWA architectures above may also use differentpath/wavelength impairment validation, which may impose differentdemands on routing. For instance, in the case where approximateimpairment information is used to validate the paths, GMPLS routing maybe used to distribute the impairment characteristics of the NEs and thelinks, e.g. based on an impairment information model. In the case of adistributed IA-RWA architecture, no changes to the routing protocol maybe necessary, but substantial changes may be needed in the signalingprotocol to enable IV. For instance, the characteristics of thetransported signal in the distributed scheme, such as the signalmodulation type, may affect system tolerance to optical impairments.Therefore, it may be advantageous to communicate such signalcharacteristics in the distributed scheme, e.g. via signaling.

Further, the different IA-RWA architectures above may comprise differentPCE configurations, which may depend on the specific functionalitiesrequired for each architecture. For instance, in the case of thecombined IA-RWA architecture 200, a single PCE (e.g. PCE 220) mayperform all the computations needed for IA-RWA. As such, the PCE may beconfigured to maintain, e.g. in a TED, information about network (e.g.WSON) topology and switching capabilities, network WDM link wavelengthutilization, and network impairment information. The PCE may also beconfigured to receive a path computation request from a PCC that maycomprise a source node, a destination node, and a signal characteristic,type, and/or required quality. If the path computation is successful,the PCE may send a reply (or response) to the PCC that may comprise thecomputed path(s) and the assigned wavelength(s). Otherwise, if the pathcomputation is not successful, the PCE may send a response to the PCCthat indicates the reason that the path computation failed. For example,the response may indicate that the path computation failed due to lackof available wavelengths, due to impairment considerations, or both.

In the case of the separate IA-RWA architectures, such as the separateIA-RWA architecture 500, at least two PCEs (e.g. the PCE 520 and PCE522) may perform the IV and RWA separately. One of the PCEs (e.g. PCE522) may be configured to perform RWA computations and coordinate theoverall IA-RWA process and the other PCE (e.g. PCE 520) may beconfigured to perform IV for candidate paths (IV-Candidate). The RWA PCEmay interact with a PCC to receive path computation requests and withthe IV-Candidates PCE to perform IV as needed and obtain a valid set ofpaths and wavelengths. The RWA PCE may also be configured to maintain,e.g. in a TED, information about network (e.g. WSON) topology andswitching capabilities and about network WDM link wavelengthutilization. However, the IV RWA PCE may not maintain impairmentinformation.

The RWA PCE may also be configured to receive a path computation requestfrom a PCC that may comprise a source node, a destination node, and asignal characteristic, type, and/or required quality. If the pathcomputation is successful, the RWA PCE may send a reply (or response) tothe PCC that may comprise the computed path(s) and the assignedwavelength(s). Otherwise, if the path computation is not successful, theRWA PCE may send a response to the PCC that indicates the reason thatthe path computation had failed. For example, the response may indicatethat the path computation had failed due to lack of availablewavelengths, due to impairment considerations, or both. Additionally,the RWA PCE may be configured to send a request to the IV-Candidates PCEto ask for K paths and acceptable wavelengths for the paths between thesource node and the destination node in the PCC request. Accordingly,the RWA PCE may receive a reply (or response) from the IV-CandidatesPCE, which may comprise at most K requested paths and associatedwavelengths between the two nodes.

The IV-Candidates PCE may be configured for impairment aware pathcomputation without necessarily the knowledge of current link wavelengthutilization. The IV-Candidates PCE may interact with the RWA PCE, butnot with the PCC, and may maintain, e.g. in a TED, information aboutnetwork (e.g. WSON) topology and switching capabilities and networkimpairment information. However, the IV-Candidates PCE may not maintainnetwork WDM link wavelength utilization. The combined IA-RWAarchitecture 400 is another IA-RWA architecture that may comprise asimilarly configured IV-Candidates PCE.

Additionally or alternatively, one of the PCEs may be configured toperform detailed IV (IV-Detailed), such as in the separate IA-RWAarchitecture 600. The IV-Detailed PCE may maintain, e.g. in a TED,network impairment information and possibly information about WDM linkwavelength utilization. To coordinate overall IA-RWA, the RWA PCE maysend an IV request to the IV-Detailed PCE, which may comprise a list ofpaths and wavelengths and any signal characteristics and qualityrequirements. Thus, the IV-Detailed PCE may send back a reply (response)to the RWA PCE, which indicates whether the IV request wassuccessfully/unsuccessfully met. For example, the reply may indicate apositive/negative decision (e.g. yes/no decision). If the IV request isnot met, the IV-Detailed PCE may send a reply to the RWA PCE thatindicates the reason that the IV request failed. Consequently, the RWAPCE may determine whether to try a different signal, e.g. by modifying asignal parameter or characteristic. The combined IA-RWA architecture 300is another IA-RWA architecture that may comprise a similarly configuredIV-Detailed PCE.

FIG. 9 illustrates an embodiment of a communication method 900 between aNE, a first control plane controller, and a second control planecontroller, which may be an adjacent control plane controller. In someembodiments, the method 900 may occur between a NE, a first controlplane controller, and the PCE, for example, when the first control planecontroller sends the RWA information to the TED in the PCE. In themethod 900, the first control plane controller obtains the RWAinformation 902 from at least one NE. The NE may send the RWAinformation 902 to the first control plane controller without promptingby the first control plane controller, or the NE may send the RWAinformation 902 to the first control plane controller in response to arequest by the first control plane controller. The first control planecontroller then sends a message 904 to the second control planecontroller, where the message 904 comprises at least one of the RWAinformation described below. Specifically, the RWA information may beembodied in at least one TLV. As used herein, the term TLV may refer toany data structure that carries the RWA information. The message 904 andperhaps the TLV may also comprise a status indicator that indicateswhether the RWA information is static or dynamic. In an embodiment, thestatus indicator may indicate how long the static or dynamic statuslasts, so that the second control plane controller can know how long theRWA information is valid and/or when to expect an update. Additionallyor alternatively, the message 904 and perhaps the TLV may comprise atype indicator that indicates whether the RWA information is associatedwith a node, a link, or both.

FIG. 10 illustrates one embodiment of a link set TLV 1000. The link setTLV 1000 may be used to encode at least one type of the RWA informationdiscussed below when the RWA information is associated with at least onenode and/or link. The link set TLV 1000 may comprise an action field1002. The action field 1002 may comprise the first about eight bits ofthe TLV 1000, and may provide information regarding the linkidentifier(s) 1010. For example, when the action field 1002 is set tozero, the link identifier(s) 1010 may represent an inclusive list inthat the links identified in the link identifier(s) 1010 are the onlylinks in the link set. Similarly, when the action field 1002 is set toone, the link identifier(s) 1010 may represent an exclusive list in thatthe links identified in the link identifier(s) 1010 are the only linksthat are excluded from the link set. In contrast, when the action field1002 is set to two, the link identifiers 1010 may represent an inclusiverange in that the link set comprises the links identified in the linkidentifiers 1010 and any links there between. Moreover, when the actionfield 1002 is set to three, the link identifiers 1010 may represent anexclusive range in that the link set does not comprise the linksidentified in the link identifiers 1010 and any links there between. Insome cases, the order of the link identifiers 1010 is unimportant suchthat the link identifiers 1010 may be arranged in any order.

The link set TLV 1000 may also comprise a directionality (Dir) field1004, a format field 1006, a reserved field 1008, and at least one linkidentifier 1010. The Dir field 1004 may comprise the subsequent abouttwo bits of the TLV 1000, and may indicate the directionality of thelinks in the link set. For example, the links may be bidirectional linkswhen the Dir field 1004 is set to zero. Alternatively, the links may beingress links when the Dir field 1004 is set to one, or the links may beegress links when the Dir field 1004 is set to two. The format field1006 may comprise the subsequent about six bits of the TLV 1000, and mayindicate the format of the link identifier 1010. For example, the formatfield 1006 may indicate the link identifier 1010 is formatted as a linklocal identifier when the format field 1006 is set to zero. The reservedfield 1008 may comprise the subsequent about 16 bits of the TLV 1000,and may be used for other purposes. At least one link identifier 1010may be included in the TLV 1000, where each link identifier 1010 isabout 32 bits in length and identifies a particular link for thepurposes described herein, e.g. inclusive lists, exclusive lists,inclusive ranges, or exclusive ranges.

FIG. 11 illustrates an embodiment of a connectivity matrix TLV 1100. TheTLV 1100 may be used to indicate the connectivity matrix describedabove. The TLV 1100 comprises a connectivity field 1102, a reservedfield 1104, at least one ingress link set 1106, at least one egress linkset 1108, and optionally additional link sets 1110. The connectivityfield 1102 may comprise the first about seven bits of the TLV 1100, andmay indicate the reconfigurability of a network element. For example,the connectivity field 1102 may be set to zero when the network elementis fixed and may be set to one when the network element isreconfigurable, as is the case with a ROADM or OXC. The reserved field1104 may be the subsequent about 24 bits of the TLV 1100, and may beused for other purposes. Each ingress link set 1106 may be variable inlength, and may be one of the link sets described above. Specifically,the ingress link set 1106 may specify the ingress links for the node.Each egress link set 1108 may be variable in length, and may be one ofthe link sets described above. Specifically, the ingress link set 1106may specify the egress links for the node. The optional additional linksets 1110 may be variable in length, may be one of the link setsdescribed above, and may specify any additional links. In some cases,the order of the ingress link set 1106, the egress link set 1108, andthe optional additional link sets 1110 is unimportant such that the linksets may be arranged in any order.

The connectivity matrix TLV 1100 may be better understood by applying itto a two-degree, 40-channel ROADM as an example. The ROADM may have oneline side ingress port, one line side egress port, 40 add ports, and 40drop ports. The ports may be numbered and identified according to thelink to which they are connected, such that the line side ingress portcan be identified by link local identifier #1, the 40 add ports can beidentified by link local identifiers #2-#41, the egress line side portcan be identified by link local identifier #42, and the 40 drop portscan be identified by link local identifiers #43-#82. Within the ROADM,the line side ingress port may be connected to the line side egress portand to all of the drop ports. Similarly, the add ports may be connectedto the line side egress port, but not any of the drop ports.

FIG. 12 illustrates an example of the connectivity matrix TLV 1200 forthe ROADM described above. The TLV 1200 is similar to the TLV 1100described above and uses the link set TLVs 600 described above for theingress link sets and the egress link sets. Specifically, theconnectivity field 1202 is set to one, which may indicate that thenetwork element, e.g. the ROADM, is reconfigurable. The TLV 1200 alsocomprises four link sets: a first ingress link set 1210, a secondingress link set 1220, a first egress link set 1230, and a second egresslink set 1240. Turning to the first ingress link set 1210, the actionfield 1212 is set to zero, which may indicate that the first ingresslink set 1210 represents an inclusive list. In addition, the Dir field1214 in the first ingress link set 1210 is set to one, which mayindicate that the first ingress link set 1210 represents ingress ports.Finally, the link identifier 1216 within the first ingress link set 1210identifies link number 1. Thus, the first ingress link set 1210 mayidentify the first link set in the reconfigurable device as being asingle ingress port, namely port #1. Turning to the second ingress linkset 1220, the action field 1222 is set to two, which may indicate thatthe second ingress link set 1220 represents an inclusive range. Inaddition, the Dir field 1224 in the second ingress link set 1220 is setto one, which may indicate that the second ingress link set 1220represents ingress ports. Finally, the link identifiers 1226 within thesecond ingress link set 1220 identify link numbers 2 and 41. Thus, thesecond ingress link set 1220 may identify the second link set in thereconfigurable device as being forty ingress ports, namely ports #2-#41.

Turning to the first egress link set 1230, the action field 1232 is setto zero, which may indicate that the first egress link set 1230represents an inclusive list. In addition, the Dir field 1234 in thefirst egress link set 1230 is set to two, which may indicate that thefirst egress link set 1230 represents egress ports. Finally, the linkidentifier 1236 within the first egress link set 1230 identifies linknumber 42. Thus, the first egress link set 1230 may identify the thirdlink set in the reconfigurable device as being a single egress port,namely port #42. Turning to the second egress link set 1240, the actionfield 1242 is set to two, which may indicate that the second egress linkset 1240 represents an inclusive range. In addition, the Dir field 1244in the second egress link set 1240 is set to two, which may indicatethat the second egress link set 1240 represents egress ports. Finally,the link identifiers 1246 within the second egress link set 1240identify link numbers 43 and 82. Thus, the second egress link set 1240may identify the fourth link set in the reconfigurable device as beingforty egress ports, namely ports #43-#82.

In an embodiment, the RWA information may include a wavelength range.The wavelength range, which may also be referred to as the WDM link orfiber wavelength range, may indicate how many different wavelengths alink or port can simultaneously accept, the range of wavelengths thatthe link or port can accept, or both. For example, the wavelength rangemay be multiple wavelengths selected from a full range of wavelengths,which may indicate that the node or link can accept a plurality ofwavelengths simultaneously and is colorless in that it has nolimitations on which wavelengths it can accept. Alternatively, thewavelength range may be a single wavelength selected from a full rangeof wavelengths, which may indicate that the node or link can accept onlyone wavelength at a time, but is colorless in that it has no limitationson which wavelength it can accept. Further in the alternative, thewavelength range may be a single, fixed wavelength, which may indicatethat the node or link can accept only one wavelength at a time and iscolored or colorful in that it is limited to a single wavelength.Moreover, the wavelength range may be multiple wavelengths selected froma reduced range of wavelengths, which may indicate that the node or linkcan accept a plurality of wavelengths simultaneously and is limited inthe wavelengths it can accept, similar to wave band switching.Specifically, the node or link may be limited to a plurality ofindividual, discrete wavelengths or may be limited to a reduced range ofwavelengths. The wavelength range may be static in that wavelength rangethat a node or link can accept does not typically change once the nodeor link is installed in the network. It will be appreciated that thewavelength range for a node may be the same for the entire node or mayvary from port to port. In addition, the wavelength ranges for the nodeor for a node's port may be independent of and perhaps different fromthe wavelength ranges for the link that is coupled an individual port onthe node. Finally, the message may contain the wavelength range for eachnode, each node's ports, each fiber, or combinations thereof within thenetwork.

As previously mentioned, some optical impairment parameters may exhibita frequency dependence that needs to be accounted for over thefrequency/wavelength of the system. In at least some embodiments, anextensible encoding of such dependence takes into account generalpurpose interpolation methods such as linear interpolation, cubicsplines, etc., as well as application specific interpolation methodssuch as the 3-term and 5-term Sellmeier formulas of Appendix A of ITU-TG.650.1. The following considerations are used in the encoding offrequency dependency: 1) each parameter in a group of parameters willhave its own interpolation data, where the “type” of the parameteridentifies how many sub-parameters are in the group; 2) interpolationdata may be broken into sub-ranges of validity for a formula withparticular interpolation coefficients; 3) the type of interpolation tobe used over the sub-ranges must be specified; and 4) the assumptionthat each sub-range will make use of the same type of interpolationformula (unless this condition is too limiting).

FIG. 13 is a schematic diagram 1300 of an optical parameter frequencydependence encoding. As shown, the frequency dependence encoding ofschematic diagram 1300 comprises an “interpolation” field 1302, a “numranges” field 1304, and a “reserved” field 1306, which form a header forthe frequency dependence encoding. The “interpolation” field 1302indicates the type of interpolation to be used across a frequency rangefor the parameter. For example, a “0” value may correspond to apiecewise constant interpolation, where a single interpolation value forthe parameter is used across each sub-range. Meanwhile, a “1” value maycorrespond to a linear interpolation, where two interpolation values forthe parameter are given corresponding to the interpolation value at eachend of a frequency sub-range. Linear interpolation is used to obtain theparameter values for frequencies between the sub-range limits. Otherinterpolation types may be available and used herein.

The “num ranges” field 1304 provides an integer to indicate the numberof sub-ranges for the interpolation. The “reserved” field 1306corresponds to reserved bits. In at least some embodiments, the“interpolation” field 1302 comprises a byte (8 bits) of data, the “numranges” field 1304 comprises a byte (8 bits) of data, and the “reserved”field 1306 comprises 2-bytes (16 bits) of data.

Following the header (fields 1302, 1304, 1306), the optical parameterfrequency dependence encoding of schematic diagram 1300 comprises thefrequency ranges and interpolation data of at least one parameter orsub-parameter. As shown, field 1308 indicates a start range of a firstinterpolation range. Field 1310 indicates interpolation data for asub-parameter corresponding to the start range of field 1308. Field 1312indicates interpolation data for another sub-parameter corresponding tothe start range of field 1308. At field 1314, another frequency rangefor interpolation data of at least one parameter or sub-parameterbegins. Field 1316 indicates interpolation data for a sub-parametercorresponding to the start range of field 1314. In the schematic diagram1300, block 1318 corresponds to additional frequency ranges and/orinterpolation data. Finally, field 1320 indicates an end wavelengthcorresponding to the end of the last frequency range with interpolationdata for at least one parameter or sub-parameter. In at least someembodiments, each of the fields 1308, 1310, 1312, 1314, 1316, 1318, and1320 comprise 4-bytes (32 bits) of data. In the case of “nointerpolation,” a sub-parameter value is assumed to be valid over theentire sub-range and no additional interpolation-related parameters orcoefficients are needed.

In at least some embodiments, network element wide parameters areprovided for path computation and/or optical path impairment validation.For these network element wide parameters, IEEE 754-2008 format 32 bitfloating point numbers may be used with the units being specified. Insome embodiments, these network element wide parameters are explicitlyidentified via a code point mechanism. Table 2 shows various networkelement wide parameters with unit and range information.

TABLE 2 Parameter Unit Range Channel frequency range GHz Min, MaxChannel insertion loss deviation dB Max Ripple dB Max Channel chromaticdispersion ps/nm Min, Max Differential group delay ps Max Polarizationdependent loss dB Max Reflectance (passive component) dB Max Reconfiguretime/Switching time ms Min, Max Channel uniformity dB Max Channeladdition/removal (steady- dB Min, Max state) gain response Transientduration ms Max Transient gain increase dB Max Transient gain reductiondB Max Multichannel gain-change difference dB Max (inter-channelgain-change difference) Multichannel gain tilt (inter- dB Max channelgain-change ratio)As shown in Table 2, for each parameter, unit information and rangeinformation may be provided. If the range of a parameter is “Max”, onlythe maximum value for the parameter is given (e.g., a 32 bit IEEEfloating point number). If the range of a parameter is “Min, Max,” theminimum value and the maximum value of the parameter are given (e.g.,two 32 bit IEEE floating point numbers). It should be understood thatnot necessarily all the parameters of Table 2 are required for pathcomputation and/or optical path impairment validation. Further, some ofthe parameters are frequency dependent while others are not. Forexample, channel insertion loss deviation and channel chromaticdispersion may be frequency dependent. In such case, the opticalparameter frequency dependence encoding of FIG. 13 may be implementedfor each of these parameters.

In accordance with at least some embodiments, per port parameters may beconsidered within the category of link parameters that are typicallydisseminated by a link state protocol. Since many optical ports on adevice tend to have the same parameters, grouping these parameterstogether for conveyance is logical and may aid in interpretation. Forexample, in a high channel count ROADM with many add and drop ports, thecharacteristics of all the add ports would tend to be similar to eachother. However, the drop ports would tend to be different from eachother and the trunk (or through) ports. Accordingly, at least someembodiments provide an optional encoding scheme based on grouping commonper port parameters along with a Link Set TLV or sub-TLV to specify theset of links that share the same port parameters.

FIG. 14 is a schematic diagram 1400 of an embodiment of a link set TLVencoding for port parameters. As shown in the schematic diagram 1400, aplurality of port parameter TLVs 1404A-1404N are aggregated to a linkset TLV 1402. In at least some embodiments, per port parameters areprovided for path computation and/or optical path impairment validation.For these per port parameters, IEEE format 32 bit floating point numbersmay be used with the units being specified. In some embodiments, theseper port parameters are explicitly identified via a code pointmechanism. Table 3 shows various per port parameters with unit and rangeinformation.

TABLE 3 Parameter Unit Range Total input power range dBm Min, MaxChannel input power range dBm Min, Max Channel output power range dBmMin, Max Input reflectance (with amplifiers) dB Max Output reflectance(with amplifiers) dB Max Maximum reflectance tolerable at input dB MinMaximum reflectance tolerable at output dB Min Maximum total outputpower dBm MaxAs shown in Table 3, for each parameter, unit information and rangeinformation may be provided. If the range of a parameter is “Max”, onlythe maximum value for the parameter is given (e.g., a 32 bit IEEEfloating point number). If the range of a parameter is “Min,” only theminimum value for the parameter is given (e.g., a 32 bit IEEE floatingpoint number). If the range of a parameter is “Min, Max,” the minimumvalue and the maximum value of the parameter are given (e.g., two 32 bitIEEE floating point numbers). It should be understood that notnecessarily all the parameters of Table 3 are required for pathcomputation and/or optical path impairment validation.

In accordance with at least some embodiments, port-to-port parametersare provided for path computation and/or optical path impairmentvalidation. To specify port-to-port parameters the corresponding portpair related to the parameters needs to be specified. In someembodiments, there may be a large number of port pairs with some ofthese port pairs having the same parameter values. In such cases, theport pairs with the same parameter values may be grouped when encodingport-to-port parameters. For example, the specification data for asimple ROADM may give the insertion loss for the “through to drop ports”as a single parameter, along with a separate insertion loss parameterfor the “add to through ports.”

In accordance with at least some embodiments, port-to-port parametersmay be considered within a Connectivity Matrix TLV or sub-TLV, which isessentially a compact listing of ingress-egress port pairs. FIG. 15 is aschematic diagram 1500 of an embodiment of a connectivity matrix TLVencoding for port-to-port parameters. As shown in the schematic diagram1500, a plurality of port-to-port parameter TLVs 1504A-1504N areaggregated to a connectivity matrix TLV 1502. In at least someembodiments, the port-to-port parameters are provided for pathcomputation and/or optical path impairment validation. For theseport-to-port parameters, IEEE format 32 bit floating point numbers maybe used with the units being specified. In some embodiments, theseport-to-port parameters are explicitly identified via a code pointmechanism. Table 4 shows various port-to-port parameters with unit andrange information.

TABLE 4 Parameter Unit Range Insertion loss dB Min, Max Isolation,adjacent channel dB Min Isolation, non-adjacent channel dB Min Channelextinction dB Min Channel signal-spontaneous noise figure dB Max Channelgain dB Min, MaxAs shown in Table 4, for each parameter, unit information and rangeinformation may be provided. If the range of a parameter is “Max”, onlythe maximum value for the parameter is given (e.g., a 32 bit IEEEfloating point number). If the range of a parameter is “Min,” only theminimum value for the parameter is given (e.g., a 32 bit IEEE floatingpoint number). If the range of a parameter is “Min, Max,” the minimumvalue and the maximum value of the parameter are given (e.g., two 32 bitIEEE floating point numbers). It should be understood that notnecessarily all the parameters of Table 4 are required for pathcomputation and/or optical path impairment validation. Further, some ofthe parameters are frequency dependent while others are not. Forexample, insertion loss, channel extinction, channel signal spontaneousnoise figure, and channel gain may be frequency dependent. In such case,the optical parameter frequency dependence encoding of FIG. 13 may beimplemented for each of these parameters.

FIG. 16 illustrates an embodiment of a path computation communicationmethod 1600 between a PCC and a PCE. The PCE may be configured forcombined IA-RWA, such as in combined IA-RWA architecture 200. The method1600 may be implemented using any suitable protocol, such as the PCEP.In the method 1600, the PCC may send a path computation request 1602 tothe PCE. The request may comprise path computation information and pathcomputation constraints. For example, the path computation informationmay comprise RWA information, including wavelength constraints, andpossibly required impairment information. Further, the path computationinformation may comprise parameter dependence information as in FIG. 13,network element wide parameters, per port parameters as in FIG. 14, andport-to-port information as in FIG. 15. At 1604, the PCE calculates apath through the network, which may be based on the path computationinformation and meet the path computation constraints. For example, thePCE may perform RWA and IV based on the RWA information and theimpairment information. The PCE may then send a path computation reply1606 to the PCC. The reply 1606 may comprise the IA-RWA.

FIG. 17 illustrates an embodiment of a path computation communicationmethod 1700 between a PCC and at least two PCEs or computation entities.The two PCEs may be configured for separate RWA and IV, such as in theseparate IA-RWA architecture 500 and the separate IA-RWA architecture400. The method 1700 may be implemented using any suitable protocol,such as the PCEP. In the method 1700, the PCC may send a pathcomputation request 1702 to the RWA PCE. The request may comprise pathcomputation information and path computation constraints. For example,the path computation information may comprise RWA information, includingwavelength constraints. The path computation constraints may comprisequality constraints, e.g. between a first node (source node) and asecond node (destination node), for a signal that may be represented bya specified type (or a class) and associated parameters. Further, thepath computation information may comprise parameter dependenceinformation as in FIG. 13, network element wide parameters, per portparameters as in FIG. 14, and port-to-port information as in FIG. 15.The RWA PCE may send an IV request 1704 to the IV PCE, which may be anIV-Candidates PCE. As such, the RWA PCE may ask for K paths andacceptable wavelengths for the paths between the two nodes indicated inthe PCC request.

At 1706, the IV-Candidates PCE may perform IV, e.g. using approximatetechniques/models, to obtain a list of validated paths and associatedwavelengths. The IV-Candidates PCE may then send a reply 1708, whichcomprises the list of paths and wavelengths, to the RWA PCE. At 1710,the RWA PCE may perform RWA using the information from the IV-CandidatesPCE and the received path computation information/constraints. The RWAPCE may then send a path computation reply 1712 to the PCC, which maycomprise the IA-RWA.

FIG. 18 illustrates an embodiment of a path computation communicationmethod 1800 between a PCC and a plurality of PCEs or computationentities. The PCEs may be configured for separate RWA and IV-Candidatesand IV-Detailed processes, such as in the separate IA-RWA architecture600 and the combined IA-RWA architecture 300. The method 1800 may beimplemented using any suitable protocol, such as the PCEP. In the method1800, the steps 1802, 1804, 1806, 1808, and 1810 between the PCC, theRWA PCE, and the IV-Candidates PCE may be configured substantiallysimilar to the corresponding steps in the method 1700.

In step 1810 of the method 1800, the RWA PCE obtains the IA-RWAcalculations. However, before sending the IA-RWA to the PCC, the PC RWAmay send an IV request 1812 to the IV-Detailed PCE. As such, the RWA PCEmay request a detailed verification of the calculated paths and assignedwavelengths from the IV-Detailed PCE. At 1814, the IV-Detailed PCE mayperform IV, e.g. using detailed techniques/models, to validate thecomputed paths and corresponding wavelengths. The IV-Detailed PCE maythen send a reply 1816 to the RWA PCE, to confirm or reject eachcomputed path. The RWA PCE may update the list of paths and wavelengthsbased on the reply from the IV-Detailed PCE and then send a reply 1818to the PCC, which may comprise the final IA-RWA.

When a network comprises a plurality of PCEs, not all the PCEs withinthe network may have the ability to perform IA-RWA or RWA. Therefore,the network may comprise a discovery mechanism that allows the PCC todetermine the PCE in which to send the request, e.g. request 1602, 1702,or 1802. For example, the discovery mechanism may comprise anadvertisement from a PCC for an IA-RWA capable PCE or RWA capable PCE,and a response from the PCEs indicating whether they have suchcapability. The discovery mechanism may be implemented as part of themethods 1600, 1700, and 1800 or as a separate process.

The network components described above may be implemented on anygeneral-purpose network component, such as a computer or networkcomponent with sufficient processing power, memory resources, andnetwork throughput capability to handle the necessary workload placedupon it. FIG. 19 illustrates a typical, general-purpose networkcomponent suitable for implementing one or more embodiments of thecomponents disclosed herein. The network component 1900 includes aprocessor 1902 (which may be referred to as a central processor unit orCPU) that is in communication with memory devices including secondarystorage 1904, read only memory (ROM) 1906, random access memory (RAM)1908, input/output (I/O) devices 1910, and network connectivity devices1912. The processor may be implemented as one or more CPU chips, or maybe part of one or more application specific integrated circuits (ASICs).

The secondary storage 1904 is typically comprised of one or more diskdrives or tape drives and is used for non-volatile storage of data andas an over-flow data storage device if RAM 1908 is not large enough tohold all working data. Secondary storage 1904 may be used to storeprograms that are loaded into RAM 1908 when such programs are selectedfor execution. The ROM 1906 is used to store instructions and perhapsdata that are read during program execution. ROM 1906 is a non-volatilememory device that typically has a small memory capacity relative to thelarger memory capacity of secondary storage 1904. The RAM 1908 is usedto store volatile data and perhaps to store instructions. Access to bothROM 1906 and RAM 1908 is typically faster than to secondary storage1904.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods might beembodied in many other specific forms without departing from the spiritor scope of the present disclosure. The present examples are to beconsidered as illustrative and not restrictive, and the intention is notto be limited to the details given herein. For example, the variouselements or components may be combined or integrated in another systemor certain features may be omitted, or not implemented.

In addition, techniques, systems, subsystems, and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

1. A network component comprising: at least one processor configured toimplement a method comprising: transmitting a message to at least oneadjacent control plane controller, wherein the message comprises aType-Length-Value (TLV) having a plurality of parameters, wherein themessage comprises frequency dependency information for each of theparameters that is frequency dependent.
 2. The network component ofclaim 1, wherein the message comprises a minimum value and a maximumvalue for each of the parameters that correspond to a ranged parameter.3. The network component of claim 2, wherein the TLV comprises at leastone ranged parameter selected from the group consisting of rangednetwork element wide parameters, ranged port parameters, and rangedport-to-port parameters.
 4. The network component of claim 2, whereinthe TLV comprises at least one ranged parameter selected from the groupconsisting of a channel frequency range parameter, a channel chromaticdispersion parameter, a total input power range parameter, a channelinput power range parameter, a channel output power range parameter, aninsertion loss parameter, and a channel gain parameter.
 5. The networkcomponent of claim 1, wherein the frequency dependency information forat least one of the parameters indicates that interpolation is not usedfor a frequency range.
 6. The network component of claim 1, wherein thefrequency dependency information for at least one of the parametersindicates an interpolation type for each of a plurality of frequencysub-ranges.
 7. The network component of claim 1, wherein the TLVcomprises at least one network element wide parameter that is frequencydependent.
 8. The network component of claim 7, wherein the at least onenetwork element wide parameter is selected from the group consisting ofa channel chromatic dispersion parameter and a channel insertion lossdeviation parameter.
 9. The network component of claim 1, wherein theTLV comprises at least one port-to-port parameter provided by aconnectivity matrix TLV or sub-TLV.
 10. The network component of claim9, wherein the at least one port-to-port parameter is a frequencydependent parameter selected from the group consisting of an insertionloss parameter, a channel extinction parameter, a channelsignal-spontaneous noise figure parameter, and a channel gain parameter.11. The network component of claim 1, wherein the TLV comprises portparameters provided by a link set TLV or sub-TLV.
 12. A methodcomprising: communicating a message comprising a Type-Length-Value (TLV)to a control plane controller, wherein the TLV comprises a plurality ofparameters and frequency dependency information for each of theparameters that is frequency dependent.
 13. The method of claim 12further comprising encoding the frequency dependency information in theTLV as: a header that indicates an interpolation type and a number offrequency sub-ranges; a start wavelength field for each sub-range; andinterpolation data for each sub-range.
 14. The method of claim 12further comprising encoding each ranged parameter of the parameters inthe TLV with a minimum value and a maximum value.
 15. The method ofclaim 12 further comprising encoding each port parameter of theparameters in the TLV using a link set TLV or sub-TLV.
 16. The method ofclaim 12 further comprising encoding each port-to-port parameter of theparameters in the TLV using a matrix connectivity TLV or sub-TLV.
 17. Anapparatus comprising: a control plane controller configured tocommunicate a Type-Length-Value (TLV) to at least one adjacent controlplane controller, wherein the TLV indicates a plurality of parametersand frequency dependency information for each of the parameters that isfrequency dependent.
 18. The apparatus of claim 17, wherein the controlplane controller is configured to encode each ranged parameter of theparameters in the TLV with a minimum value and a maximum value.
 19. Theapparatus of claim 17, wherein the control plane controller isconfigured to encode each port parameter of the parameters in the TLVusing a link set TLV or sub-TLV.
 20. The apparatus of claim 17, whereinthe control plane controller is configured to encode each port-to-portparameter of the parameters in the TLV using a matrix connectivity TLVor sub-TLV.